/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *  http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.codec.language;

import com.mlizhi.base.codec.EncoderException;
import com.mlizhi.base.codec.StringEncoder;


/**
 * Encodes a string into a metaphone value. 
 * <p>
 * Initial Java implementation by <CITE>William B. Brogden. December, 1997</CITE>. 
 * Permission given by <CITE>wbrogden</CITE> for code to be used anywhere.
 * </p>
 * <p>
 * <CITE>Hanging on the Metaphone</CITE> by <CITE>Lawrence Philips</CITE> in <CITE>Computer Language of Dec. 1990, p
 * 39.</CITE>
 * </p>
 * <p>
 * Note, that this does not match the algorithm that ships with PHP, or the algorithm 
 * found in the Perl <a href="http://search.cpan.org/~mschwern/Text-Metaphone-1.96/Metaphone.pm">Text:Metaphone-1.96</a>.
 * They have had undocumented changes from the originally published algorithm. 
 * For more information, see <a href="https://issues.apache.org/jira/browse/CODEC-57">CODEC-57</a>.
 * </p>
 * 
 * @author Apache Software Foundation
 * @version $Id: Metaphone.java 797690 2009-07-24 23:28:35Z ggregory $
 */
public class Metaphone implements StringEncoder {

/**
 * Five values in the English language 
 */
private static final String VOWELS = "AEIOU" ;

/**
 * Variable used in Metaphone algorithm
 */
private static final String FRONTV = "EIY"   ;

/**
 * Variable used in Metaphone algorithm
 */
private static final String VARSON = "CSPTG" ;

/**
 * The max code length for metaphone is 4
 */
private int maxCodeLen = 4 ;

/**
 * Creates an instance of the Metaphone encoder
 */
public Metaphone() {
super();
}

/**
 * Find the metaphone value of a String. This is similar to the
 * soundex algorithm, but better at finding similar sounding words.
 * All input is converted to upper case.
 * Limitations: Input format is expected to be a single ASCII word
 * with only characters in the A - Z range, no punctuation or numbers.
 *
 * @param txt String to find the metaphone code for
 * @return A metaphone code corresponding to the String supplied
 */
public String metaphone(String txt) {
boolean hard = false ;
if ((txt == null) || (txt.length() == 0)) {
return "" ;
}
// single character is itself
if (txt.length() == 1) {
return txt.toUpperCase(java.util.Locale.ENGLISH) ;
}
  
char[] inwd = txt.toUpperCase(java.util.Locale.ENGLISH).toCharArray() ;
  
StringBuffer local = new StringBuffer(40); // manipulate
StringBuffer code = new StringBuffer(10) ; //   output
// handle initial 2 characters exceptions
switch(inwd[0]) {
case 'K' : 
case 'G' : 
case 'P' : /* looking for KN, etc*/
if (inwd[1] == 'N') {
local.append(inwd, 1, inwd.length - 1);
} else {
local.append(inwd);
}
break;
case 'A': /* looking for AE */
if (inwd[1] == 'E') {
local.append(inwd, 1, inwd.length - 1);
} else {
local.append(inwd);
}
break;
case 'W' : /* looking for WR or WH */
if (inwd[1] == 'R') {   // WR -> R
local.append(inwd, 1, inwd.length - 1); 
break ;
}
if (inwd[1] == 'H') {
local.append(inwd, 1, inwd.length - 1);
local.setCharAt(0, 'W'); // WH -> W
} else {
local.append(inwd);
}
break;
case 'X' : /* initial X becomes S */
inwd[0] = 'S';
local.append(inwd);
break ;
default :
local.append(inwd);
} // now local has working string with initials fixed

int wdsz = local.length();
int n = 0 ;

while ((code.length() < this.getMaxCodeLen()) && 
   (n < wdsz) ) { // max code size of 4 works well
char symb = local.charAt(n) ;
// remove duplicate letters except C
if ((symb != 'C') && (isPreviousChar( local, n, symb )) ) {
n++ ;
} else { // not dup
switch(symb) {
case 'A' : case 'E' : case 'I' : case 'O' : case 'U' :
if (n == 0) { 
code.append(symb);
}
break ; // only use vowel if leading char
case 'B' :
if ( isPreviousChar(local, n, 'M') && 
 isLastChar(wdsz, n) ) { // B is silent if word ends in MB
break;
}
code.append(symb);
break;
case 'C' : // lots of C special cases
/* discard if SCI, SCE or SCY */
if ( isPreviousChar(local, n, 'S') && 
 !isLastChar(wdsz, n) && 
 (FRONTV.indexOf(local.charAt(n + 1)) >= 0) ) { 
break;
}
if (regionMatch(local, n, "CIA")) { // "CIA" -> X
code.append('X'); 
break;
}
if (!isLastChar(wdsz, n) && 
(FRONTV.indexOf(local.charAt(n + 1)) >= 0)) {
code.append('S');
break; // CI,CE,CY -> S
}
if (isPreviousChar(local, n, 'S') &&
isNextChar(local, n, 'H') ) { // SCH->sk
code.append('K') ; 
break ;
}
if (isNextChar(local, n, 'H')) { // detect CH
if ((n == 0) && 
(wdsz >= 3) && 
isVowel(local,2) ) { // CH consonant -> K consonant
code.append('K');
} else { 
code.append('X'); // CHvowel -> X
}
} else { 
code.append('K');
}
break ;
case 'D' :
if (!isLastChar(wdsz, n + 1) && 
isNextChar(local, n, 'G') && 
(FRONTV.indexOf(local.charAt(n + 2)) >= 0)) { // DGE DGI DGY -> J 
code.append('J'); n += 2 ;
} else { 
code.append('T');
}
break ;
case 'G' : // GH silent at end or before consonant
if (isLastChar(wdsz, n + 1) && 
isNextChar(local, n, 'H')) {
break;
}
if (!isLastChar(wdsz, n + 1) &&  
isNextChar(local,n,'H') && 
!isVowel(local,n+2)) {
break;
}
if ((n > 0) && 
( regionMatch(local, n, "GN") ||
  regionMatch(local, n, "GNED") ) ) {
break; // silent G
}
if (isPreviousChar(local, n, 'G')) {
// NOTE: Given that duplicated chars are removed, I don't see how this can ever be true
hard = true ;
} else {
hard = false ;
}
if (!isLastChar(wdsz, n) && 
(FRONTV.indexOf(local.charAt(n + 1)) >= 0) && 
(!hard)) {
code.append('J');
} else {
code.append('K');
}
break ;
case 'H':
if (isLastChar(wdsz, n)) {
break ; // terminal H
}
if ((n > 0) && 
(VARSON.indexOf(local.charAt(n - 1)) >= 0)) {
break;
}
if (isVowel(local,n+1)) {
code.append('H'); // Hvowel
}
break;
case 'F': 
case 'J' : 
case 'L' :
case 'M': 
case 'N' : 
case 'R' :
code.append(symb); 
break;
case 'K' :
if (n > 0) { // not initial
if (!isPreviousChar(local, n, 'C')) {
code.append(symb);
}
} else {
code.append(symb); // initial K
}
break ;
case 'P' :
if (isNextChar(local,n,'H')) {
// PH -> F
code.append('F');
} else {
code.append(symb);
}
break ;
case 'Q' :
code.append('K');
break;
case 'S' :
if (regionMatch(local,n,"SH") || 
regionMatch(local,n,"SIO") || 
regionMatch(local,n,"SIA")) {
code.append('X');
} else {
code.append('S');
}
break;
case 'T' :
if (regionMatch(local,n,"TIA") || 
regionMatch(local,n,"TIO")) {
code.append('X'); 
break;
}
if (regionMatch(local,n,"TCH")) {
// Silent if in "TCH"
break;
}
// substitute numeral 0 for TH (resembles theta after all)
if (regionMatch(local,n,"TH")) {
code.append('0');
} else {
code.append('T');
}
break ;
case 'V' :
code.append('F'); break ;
case 'W' : case 'Y' : // silent if not followed by vowel
if (!isLastChar(wdsz,n) && 
isVowel(local,n+1)) {
code.append(symb);
}
break ;
case 'X' :
code.append('K'); code.append('S');
break ;
case 'Z' :
code.append('S'); break ;
} // end switch
n++ ;
} // end else from symb != 'C'
if (code.length() > this.getMaxCodeLen()) { 
code.setLength(this.getMaxCodeLen()); 
}
}
return code.toString();
}

private boolean isVowel(StringBuffer string, int index) {
return VOWELS.indexOf(string.charAt(index)) >= 0;
}

private boolean isPreviousChar(StringBuffer string, int index, char c) {
boolean matches = false;
if( index > 0 &&
index < string.length() ) {
matches = string.charAt(index - 1) == c;
}
return matches;
}

private boolean isNextChar(StringBuffer string, int index, char c) {
boolean matches = false;
if( index >= 0 &&
index < string.length() - 1 ) {
matches = string.charAt(index + 1) == c;
}
return matches;
}

private boolean regionMatch(StringBuffer string, int index, String test) {
boolean matches = false;
if( index >= 0 &&
(index + test.length() - 1) < string.length() ) {
String substring = string.substring( index, index + test.length());
matches = substring.equals( test );
}
return matches;
}

private boolean isLastChar(int wdsz, int n) {
return n + 1 == wdsz;
} 


/**
 * Encodes an Object using the metaphone algorithm.  This method
 * is provided in order to satisfy the requirements of the
 * Encoder interface, and will throw an EncoderException if the
 * supplied object is not of type java.lang.String.
 *
 * @param pObject Object to encode
 * @return An object (or type java.lang.String) containing the 
 * metaphone code which corresponds to the String supplied.
 * @throws EncoderException if the parameter supplied is not
 *  of type java.lang.String
 */
public Object encode(Object pObject) throws EncoderException {
if (!(pObject instanceof String)) {
throw new EncoderException("Parameter supplied to Metaphone encode is not of type java.lang.String"); 
}
return metaphone((String) pObject);
}

/**
 * Encodes a String using the Metaphone algorithm. 
 *
 * @param pString String object to encode
 * @return The metaphone code corresponding to the String supplied
 */
public String encode(String pString) {
return metaphone(pString);   
}

/**
 * Tests is the metaphones of two strings are identical.
 *
 * @param str1 First of two strings to compare
 * @param str2 Second of two strings to compare
 * @return <code>true</code> if the metaphones of these strings are identical, 
 *<code>false</code> otherwise.
 */
public boolean isMetaphoneEqual(String str1, String str2) {
return metaphone(str1).equals(metaphone(str2));
}

/**
 * Returns the maxCodeLen.
 * @return int
 */
public int getMaxCodeLen() { return this.maxCodeLen; }

/**
 * Sets the maxCodeLen.
 * @param maxCodeLen The maxCodeLen to set
 */
public void setMaxCodeLen(int maxCodeLen) { this.maxCodeLen = maxCodeLen; }

}
